I was able to solve the overwriting. Thanks.
But I am having trouble with the mail server being recognized.
I have two servers
example.com on Digital Ocean which works
System hostname host.example.com (127.0.0.1) (on webmin dashboard)
; Created by cloud-init on instance boot automatically, do not edit
example1.com on AWS Lightsail which does not work
System hostname host.example1.com (34.228.125.xxx) (on webmin dashboard)
I suspect that the I might need “127.0.0.1” instead of “34.228.125.xxx” for the system hostname and need to add “Local hostname” to the Resolution order for example1.com
But I am stumped how to do this or make other needed changes.
Help would be appreciated.